A touch device has an advantage of easy operation. Recently, the touch device has been widely applied to various electronic products, for example, mobile phones, personal digital assistants (PDAs), digital cameras, music players, computers, satellite navigation devices, touch screens, and so on. Generally, a familiar type of the touch device is, for example, a resistive touch device a capacitive touch device or an optical touch device. The optical touch device has a lower cost comparative to the resistive touch device or the capacitive touch device.
FIG. 1 is a schematic, cross-sectional view of a conventional optical touch device. Referring to FIG. 1, the conventional optical touch device 100 includes a transparent substrate 110, two linear light sources 120 and two light sensing components 130. Only one of the two linear light sources 120 and only one of the two light sensing components 130 are shown in FIG. 1. The transparent substrate 110 is rectangular. The two linear light sources 120 respectively correspond to the two light sensing components 130 one by one. The linear light source 120 and the corresponding light sensing component 130 are respectively disposed at two opposite sides of the transparent substrate 110. Each of the linear light sources 120 is disposed beside a light incidence surface 112 of the transparent substrate 110, and each of the light sensing components 130 is disposed beside a light emitting surface 114 of the transparent substrate 110. In addition, a lens set 140 is disposed between each of the light sensing components 130 and the corresponding light emitting surface 114.
Each of the linear light sources 120 of the conventional optical touch device 100 includes a light emitting diode 122 for providing a plurality of optical signals 123. The optical signals 123 enter into the transparent substrate 110 through the light incidence surface 112. Then, a portion of the optical signals 123 is totally reflected many times in the transparent substrate 110 to emit from the light emitting surface 114. The lens set 140 is configured for receiving the portion of the optical signals 123 and congregating the portion of the optical signals 123 to the light sensing component 130. When a touch surface 116 of the transparent substrate 110 is touched by a touch member 50 (e.g., a finger or a pen), the portion of the optical signals 123 arriving at a portion of the touch surface 116 touched by the touch member 50 can not be totally reflected and can not be sensed by the light sensing components 130. Thus, a location of the touch member 50 along an axis can be obtained according to a location of a portion of a sensing region of each of the light sensing components 130 where the optical signals 123 is not sensed. Therefore, the exact location of the touch member 50 on the touch surface 116 can be obtained according to the information sensed by the two light sensing components 130.
However, in the conventional optical touch device 100, the optical signals 123 have different incidence angles while striking at the light incidence surface 112 to enter into the transparent substrate 110 through the light incidence surface 112. Thus, a light incidence efficiency of the optical signals 123 is low. Moreover, a portion of the optical signals 123 emits out of the transparent substrate 110 from the light emitting surface 114 without total reflections in the transparent substrate 110 so that the light sensing components 130 can not sensing the optical signals 123 exactly. Additionally, the optical signals 123 emits out of the transparent substrate 110 from the light emitting surface 114 have different emitting angles. Thus, a light congregating efficiency of the lens set 140 is low, thereby affecting the sensing effect of the corresponding light sensing component 130.